<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>下拉菜单</title>
    <link href="bootstrap-3.3.7-dist/css/bootstrap.min.css" rel="stylesheet">
    <script src="jquery-3.2.1.js"></script>
    <script src="bootstrap-3.3.7-dist/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
    <nav class="nav navbar-default">
        <div class="navbar-header">
            <a class="navbar-brand" href="#">W3Cschool</a>
        </div>

        <div id="myexample">
            <ul class="nav navbar-nav">
                <li class="active"><a href="#">iOS</a> </li>
                <li><a href="#">SVN</a> </li>
                <li class="dropdown">
                    <a href="#" class="dropdown-toggle" data-toggle="dropdown">Java<b class="caret"></b> </a>
                    <ul class="dropdown-menu">
                        <li><a id="action-1" href="#">jmeter</a></li>
                        <li><a href="#">EJB</a></li>
                        <li><a href="#">Jasper Report</a></li>
                        <li class="divider"></li>
                        <li><a href="#">分离的链接</a></li>
                        <li class="divider"></li>
                        <li><a href="#">另一个分离的链接</a></li>
                    </ul>
                </li>
            </ul>
        </div>
    </nav>
</div>

<script>
    $(function () {
       $(".dropdown-toggle").dropdown('toggle');
    });
</script>
</body>
</html>